Artificial culture technology of baby fish

Dazhu, commonly known as baby fish, is a specialty of our country, so it is also known as Chinese giant salamander. Giant salamander is distributed all over China, mainly in the deep mountains and dense forests and streams in South China and Southwest China. The common individual weighs 2-5kg, the body length is about 50~150cm, and the largest individual can reach 10~20kg. Giant salamander has high edible and medicinal value because of its delicate meat, delicious taste and rich nutrition. In recent years, due to man-made indiscriminate fishing and serious damage to the natural ecological environment, the resources of giant salamander are decreasing day by day, and they are frequently endangered animals, so they are listed as the second category of key protected wild animals by the state. Therefore, it is of great practical significance to study and discuss the biological characteristics, artificial reproduction and culture technology of giant salamander.

Biological characteristics of giant salamander

1. Morphological characteristics.

Artemisia belongs to amphibia, cauda, Cryptobranchidae, with bare body surface, smooth and elastic skin, covered with irregular dots or patches of cyan-gray pigment, and body color often changes due to the change of environment. The abdomen is grayish white, the head is wide and flat, the mouth is slightly semi-circular, the plough bone and jaw have teeth, the plough bone teeth are more developed, it is the main tool to catch food, the adult does not have Gill, breathe with lungs, the eyes are distributed on both sides of the head, the eye septum is wide and flat, no eyelids, one on each side of the nostril, small and circular, located above the eyes. The vertebral body is doubly concave, the abdomen is obese, accounting for about 1 of the body length, and there is an inconspicuous degenerated dorsal fin extending to the tail on the back. The giant salamander has a pair of front and hindlimb, 4 fingers of the forelimb and 5 toes of the hindlimb, and the limb shape is similar to that of the frog limb. The exercise of the giant salamander is mainly completed by the limbs, there is a lifetime reproductive pore between the abdomen of the two hind limbs, the outer end coincides with the excretory foramen, and the female salamander does not have a fertilizer.

2. Life habits

Magnolia is a variable temperature animal, which often lives in streams with deep mountains and dense forests. It likes to live in the middle and lower layers of the water. It can survive in the water of 0: 38 ℃. The suitable water temperature is 16-28 ℃. When the water temperature is lower than 14 ℃ and higher than 33 ℃, the food intake decreases, the action is slow, and the growth is slow. When the water temperature is below 10 ℃, hibernation begins and food is stopped completely. The giant salamander has relatively strict requirements for dissolved oxygen and water quality in the water. When the dissolved oxygen in the water is above 5mg/L, the water quality is fresh and pollution-free, which is most suitable for the growth and development of giant salamander, especially in the incubation and larval stage. The dissolved oxygen in the water must be kept above 5.5mg/L, and the water in the seedling pond remains in a normal flow state. The suitable range of PH value is 6.0-9.0, and the optimum PH value is 6.8-8.2. In the natural ecological environment, giant salamander often camp benthic life, living in seclusion in the cave during the day, crawling out of the cave to find food at night, and like the dark, afraid of bright light and shock. Often feed on small fish, shrimps and other aquatic animals in streams, can eat fish equivalent to their own length of 1 stroke 2 fish, feeding fish are generally wheat ear fish, goby fish, mackerel fish, bouquet fish, Douyu, Loach, snakehead, and mollusks such as snails, clams, etc., and prey on aquatic insects, water rats, water snakes, frogs and other animals. Under the condition of artificial culture, in addition to feeding on a variety of wild fish, it can also feed on some animal carcasses, animal blood or internal organs. Artificial formula feed can also be ingested through domestication.

3. Growth characteristics and reproductive habits.

Under the natural environmental conditions, due to the good water quality and rich bait resources, the giant salamander grows faster, and the largest individual can reach 10~15kg. Under the condition of artificial culture, the growth rate was the fastest at the age of 2 to 5 years old, especially at the age of 2 years, the annual growth times of body weight and body length were 6.5 to 9.8 and 2.2 respectively. The body weight of pond-raised giant salamander is obviously faster than that of wild population, which is mainly related to the comprehensive nutrition of artificial feeding and suitable water temperature, and does not hibernate even in severe winter. Under natural conditions, sexual maturity is generally reached at 4 years old, and under artificial culture conditions, female salamanders reach sexual maturity at 4 ~ 5 years old. When the giant salamander is sexually mature, squeezing the abdomen of the male salamander can excrete milky semen, which can be dispersed by dripping into the water, and the female salamander can produce long-chain rosary-shaped zonal eggs that can be fertilized in vitro during reproduction. May-September is the breeding period of giant salamander. During the breeding season, giant salamander often makes doll-like calls. The optimum water temperature for hatching and breeding is 22-25 ℃. The artificial reproduction of giant salamander has been studied for nearly 30 years in our country. so far, the artificial reproduction of giant salamander has made little progress, the success rate is very low, and the source of seedlings is still mainly natural resources. to carry out the research on the artificial reproduction technology of giant salamander is an important topic and main direction in the future.

4. Seedling identification in amphibia, the Cryptobranchidae giant salamander in the caudate order is very similar to the small salamander family, salamander family and cave salamander family. In recent years, stimulated by the high profits of giant salamander seedlings, some seedling suppliers mix beads with fish eyes. The adults of the spotless salamander or small salamander family are often sold as giant salamander seedlings, causing losses to breeders. In order to distinguish giant salamander from salamander and salamander, their morphological characteristics are compared as follows for reference in identification.

Artificial culture of giant salamander

1. Construction of aquaculture pond

Giant salamander culture pond can be designed according to the characteristics of the terrain, often designed to form an oval shape of two, its area is generally 200-300m2 is appropriate, to do a good job in the installation of drainage pipes, the design of water pipes should be higher than the drainage pipe, generally about 80cm from the bottom of the pool, in the inlet pipe mouth can be installed "duck bill" with tin processing or trapezoid, wide edge for water outlet, "duck mouth" outlet about 1cm thick, 20cm wide. According to the area of the culture pond, the number of duck beaks is determined, which can not only reduce foreign debris, but also increase the width of the influent water surface and promote the circulation of the water body in the pond. The installation of the drainage pipe should be close to the bottom of the pool to facilitate the removal of deposited dirt. The height of the pool is 2.5cm, and the wall of the pool is coated with cement to keep it as smooth as possible. Several artificial caves are built with bricks, cement boards and other materials in the culture pond. the length, width and height of the cave are 2mm 4m, 1m and 0.5m respectively, and the cave can also be connected with each other, but the cave wall should be kept smooth as far as possible so as not to scratch the skin of the body. The soil quality should be the best for the cave and pool bottom, and the ratio of sand and pebble with 20cm thickness to river sand should be 5 ∶ 1, and a bait platform should be set up above the cave. The feed platform is required to be flat, and its area accounts for about 30% of the culture pond, and the slope ratio on both sides is 1 ∶ 5. Cover the shade shed with blue fiber tiles above the bait table to prevent the giant salamander from being frightened when eating. After the new aquaculture pond is completed, the pond water should be filled with a depth of about 2m, and after 3-4 days, it should be drained, and then re-filled with new water, so that after repeated 3-4 times, the alkalinity of cement will disappear completely and when there is a layer of attachment on the pool wall and cave wall, you can breed. In order to ensure the supply of fresh bait, a bait pool can be built nearby, in which a certain number of fertile and easy-to-raise fish and molluscs, frogs such as tilapia, wheat ear fish, snails, clams and small tadpoles can be used as bait for giant salamanders.

2. Seed stocking

In order to prevent the pathogenic microorganisms on the body surface of Andrias davidianus from being brought into the salamander pond, the seedlings of giant salamander were disinfected with 1% concentration of gentian purple medicine solution. The method was that after the ratio of medicine to water was 1 ∶ 100, the seeds were soaked in the medicine solution for 15 minutes, and then put into the culture pond for artificial feeding. The stocking density is 5 species of 8~10cm and 4 species of 11~20cm per 10m2 water body. At this stage, most of the species are collected from nature, and the sizes are very different. therefore, we should do a good job in the screening of seedlings during stocking, and try our best to breed species of the same specification in each culture pond, which can avoid bullying and killing each other, and improve the survival rate of raising salamanders.

3. Bait

Giant salamanders feed on animal bait, which is not only rich in protein, but also rich in zinc, iron, calcium, phosphorus, and various trace elements. Artificial feeding should strive to be more extensive and match well. In addition to feeding a certain amount of live bait such as wild fish, shrimp, tadpoles and mussels, animals should also be properly fed with viscera, blood clots, scraps and so on. The feeding method is that according to the individual size and feeding condition of the giant salamander, first wash the animal internal organs and use a meat grinder to grind the animal internal organs to the required fineness and put them on the bait table. The bait table should be cleaned before each feeding to ensure the cleanliness and hygiene of the bait table, and the animal viscera, blood clots and scraps should not be directly thrown into the water body, which will not only reduce the utilization rate of bait, but also easily cause water pollution. When feeding fresh bait, fish and shrimp, snail mussels or tadpoles can be put into the culture pond directly to allow the giant salamander to hunt freely, which can greatly improve the utilization rate of bait and increase food intake. The giant salamander has the habit of sleeping during the day and going out at night, and the feeding time should be determined in the evening. In the process of feeding, the giant salamander should avoid disturbance, because the giant salamander has the behavior of "vomiting" after being stimulated by shock.

4. Regulation of water quality and water temperature

The water quality of salamander ponds should always be kept fresh and pollution-free. With the increase of individual and food intake of giant salamander in summer and autumn, a large number of excreta will increase, which can easily cause water quality to deteriorate. Therefore, in addition to the regular removal of residual bait and excrement in the pool, the pool water should be changed regularly, generally every 3 to 4 days, and the amount of water each time is 1 pound 3 of the pool water. If the water source is abundant, it can ensure that there is constant running water in the giant salamander culture pond, which is more beneficial to the growth and development of the giant salamander, especially in the breeding season of the giant salamander, which can stimulate the nervous system of the giant salamander, promote gonadal development and improve the reproduction rate. In addition, a certain number of snails can be raised in the salamander pond. Because the snail can feed on the humus at the bottom of the pond, it can not only remove the dirt in the pond, but also provide palatable bait for the giant salamander. The transparency of pool water is generally about 35cm, and the dissolved oxygen in water is above 5mg/L. In order to control the PH value of the water body up to 6.78, it is adjusted by sprinkling quicklime according to the specific situation. Water temperature is also very important to the growth and development of giant salamander. The most suitable water temperature is 22-25 ℃. In hot summer, mountain stream water or clear spring water should be introduced into salamander pond as much as possible to avoid summer heat, and the pool water should be properly deepened to about 2m. In order to prevent direct sunlight exposure, some aquatic plants such as water hyacinth, duckweed and water lotus can be raised in the pond, and vines can be planted around the culture pond, which can effectively control the sudden change of water temperature in the pond. In early winter, giant salamander hibernates when the water temperature drops below 10 ℃. Under artificial breeding conditions, in order to promote the rapid growth and development of giant salamander, a series of methods such as geothermal water, industrial warm water or building greenhouse heating are generally used to adjust the water temperature in the pond, so that the water temperature is often constant at 20: 28 ℃ so that the giant salamander can still eat and grow normally in winter, which is also one of the keys to improve the yield of salamander.

5. Disease control

In the process of artificial culture, due to the change of the ecological environment and living habits of giant salamander, the water quality is easy to be polluted, coupled with the incomplete nutrition of the feed and the relative increase of stocking density, which will increase the probability of bacterial infection. Whenever there is a lack of bait, it often causes the fighting bite of the giant salamander to be easily injured. According to relevant data, the incidence of artificial breeding giant salamander is more than tens of times higher than that of wild population. The common diseases of giant salamander are skin rot disease and rotting tail disease, which are introduced as follows.

① rotten tail disease: when giant salamander suffers from this disease, the base of the tail stalk to the end of the tail often shows red spots or red spots, the surrounding skin tissue is congested and inflamed, the epidermis is slightly grayish white, and in severe cases, the diseased tissue muscle necrosis, tail bone exposure, often with dark red or yellowish liquid from the trauma site. Sick salamander activity weakens or lying on the ground does not move, do not think about food, the tail becomes stiff, and soon dies. The disease can occur in four seasons, and the peak of the disease is from June to August, which mainly harms the 1-year-old and 3-year-old giant salamander. Prevention and treatment: sprinkle with 0.2~0.3ppm chlorine dioxide in the whole pool, including bait table and artificial cave, once a day, 3-4 days as a course of treatment. For the seriously ill giant salamander, the wound site was first washed with 15~25ppm concentration potassium permanganate solution, and the attachment on the wound surface was cleaned with cotton balls, then the affected area was coated with anti-inflammatory drugs such as Xiaojilong ointment or sulfur ointment, once a day for 5-7 days as a course of treatment, combined with chloramphenicol 2mg + kana powder 2g+Vc2g+VE2g+VB2g per kg body weight. The above drugs were evenly mixed into the bait and fed for 4 days.

② skin rot: a disease caused by Aeromonas hydrophila. Its symptoms are as follows: irregular red masses often appear on the body surface of the disease. At the beginning of the disease, there are yellowish purulent cysts in the center of the red masses, and gradually spread to the surrounding skin tissue. When the pus breaks through, it forms a scabies-like focus, and the focus tissue is congested and inflamed, showing a raging shape. At this time, the infection is quite fast, and the sick salamander lies down in the pool and does not eat. If no measures are taken for timely treatment, the mortality rate is higher. Prevention and cure method: sprinkle the whole pond with 0.3~0.4ppm strong chlorine essence or 0.2~0.3ppm chlorine dioxide regularly and carry on the thorough disinfection and sterilization treatment. The disease occurred once a day for 4-6 days, and the affected area was washed with 0.3~0.5ppm malachite green solution or medical hydrogen peroxide, and then applied with Xiaozhilong ointment or Fuyankang ointment, once a day for 4-7 days as a course of treatment. Then according to the body weight of giant salamander every kilogram of turtle Baokang injection 0.3~0.4mL, the injection site is generally the lower part of the forelimb soft tissue, at an angle of 45 degrees, once a day, continuous use of 3-4 days can be cured. Note: when it is found that the giant salamander is sick, the sick salamander should be quickly isolated and raised in separate ponds.